推导式¶

squares = []               # 创建空列表squares
for x in range(10):        # x依次取0-10中的数字
    squares.append(x**2)   # 向列表中增加x的平方
print(squares)       # 输出列表squares，[0, 1, 4, 9, 16, 25, 36, 49, 64, 81]
#用lambda函数实现，将0-9中每个数映射为其平方并转为列表
squares = list(map(lambda x: x**2, range(10)))   
print(squares)       # 输出列表squares，[0, 1, 4, 9, 16, 25, 36, 49, 64, 81]

squares = [x**2 for x in range(10) if x%2 == 0]#计算range(10)中每个数的平方，推导出新列表
print(squares)      # 输出新列表squares，[0, 1, 4, 9, 16, 25, 36, 49, 64, 81]

def fun(x):
    return x + x ** 2 + x ** 3     # 返回x + x ** 2 + x ** 3

y = [fun(i) for i in range(10)]    # 列表推导式，按函数fun(x)，推导出新列表
print(y)               # 输出列表[0, 3, 14, 39, 84, 155, 258, 399, 584, 819]

def fun(x):
    return x + x**2 + x ** 3  # 返回x + x ** 2 + x ** 3

# 列表推导式，根据原列表中的偶数，推导新列表
y = [fun(i) for i in range(10) if i%2 == 0]  
print(y)                                     # 输出列表[0, 14, 84, 258, 584]

ls = [(x, y) for x in [1,2,3] for y in [3,1,4] if x != y]
print(ls)      # 输出[(1, 3), (1, 4), (2, 3), (2, 1), (2, 4), (3, 1), (3, 4)]

ls = [-4, -2, 0, 2, 4]
print([x*2 for x in ls])# 将原列表每个数字乘2，推导出新列表 [-8, -4, 0, 4, 8]
print([x for x in ls if x >= 0])   # 过滤列表，返回只包含正数的列表[0, 2, 4]
print([abs(x) for x in ls])        # 应用abs()函数推导新列表[4, 2, 0, 2, 4]
# 调用strip()方法去除每个元素前后的空字符,返回['banana', 'apple', 'pear']
freshfruit = ['  banana', '  apple ', 'pear  ']
print([fruit.strip() for fruit in freshfruit]) #
# 生成一个每个元素及其平方(number, square)构成的元组组成的列表
print([(x, x**2) for x in range(6)]) 
# [(0, 0), (1, 1), (2, 4), (3, 9), (4, 16), (5, 25)]

# 鄂A.27F37
# 鄂A.2737F
license_plate = input()

# 鄂A.27F37->2737
license_plate_int = int(''.join([x for x in license_plate if x.isdigit()]))
if license_plate_int % 2 == 0:
    print('限行')
else:
    print('允许通行')

txt = '''
I Want Nothing 我一无所求

Tagore 泰戈尔



I asked nothing， 

only stood at the edge of the wood behind the tree.　　

我一无所求，

只站在林边树后。 

Languor was still upon the eyes of the dawn， 

and the dew in the air.　　

倦意还逗留在黎明的眼上，

露润在空气里。 

The lazy smell of the damp grass hung in the thin mist above the earth.　　

湿草的懒味悬垂在地面的薄雾中。　

Under the banyan tree you were milking the cow with your hands，

 tender and fresh as butter.　　

在榕树下你用乳油般柔嫩的手挤着牛奶。　

And I was standing still.　　

我沉静地站立着。　　



I did not come near you.　　

我没有走近你。　　

The sky woke with the sound of the gong at the temple.　　

天空和庙里的锣声一同醒起。　　



The dust was raised in the road from the hoofs of the driven cattle.　　

街尘在驱走的牛蹄下飞扬。　　



With the gurgling pitchers at their hips， 

women came from the river.　　

把汩汩发响的水瓶搂在腰上，

女人们从河边走来。　

Your bracelets were jingling， 

and foam brimming over the jar.　　

你的钏镯丁当，

乳沫溢出罐沿。　

The morning wore on and I did not come near you.　　

晨光渐逝而我没有步近你。
'''

txt_en = ''.join([c for c in txt if ord(c)<128])
print(txt_en)

# 先得到二维列表
[[0, 'Italy', "Aromas include tropical fruit, broom, brimstone and dried herb. The palate isn't overly expressive, offering unripened apple, citrus and dried sage alongside brisk acidity.", 87, 13.0, 'Sicily & Sardinia'], 
 [10, 'US', 'Soft, supple plum envelopes an oaky structure in this Cabernet, supported by 15% Merlot. Coffee and chocolate complete the picture, finishing strong at the end, resulting in a value-priced wine of attractive flavor and immediate accessibility.', 87, 19.0, 'California'], 
 [20, 'US', 'Ripe aromas of dark berries mingle with ample notes of black pepper, toasted vanilla and dusty tobacco. The palate is oak-driven in nature, but notes of tart red currant shine through, offering a bit of levity.', 87, 23.0, 'Virginia'], 
 [30, 'France', 'Red cherry fruit comes laced with light tannins, giving this bright wine an open, juicy character.', 86, 15.0, 'Beaujolais'], 
 [40, 'Italy', "Catarratto is one of Sicily's most widely farmed white grape varieties. This expression shows a mineral note, backed by citrus and almond blossom touches.", 86, 17.0, 'Sicily & Sardinia'],
 [50, 'Italy', "This blend of Nero d'Avola and Syrah opens with savory aromas of cured meat, dried berry, cassis, tobacco and wet earth. There's a touch of almond bitterness on the finish.", 86, 15.0, 'Sicily & Sardinia'], 
 [60, 'US', 'Syrupy and dense, this wine is jammy in plum and vanilla, with indeterminate structure and plenty of oak. Ripe and full-bodied, it has accents of graphite and leather.', 86, 100.0, 'California'], 
 [70, 'US', 'Aromas of vanilla, char and toast lead to light creamy stone fruit and canned-corn flavors. It provides appeal but the oak seems overweighted.', 86, 12.0, 'Washington'],
 [80, 'Chile', 'Caramelized oak and vanilla aromas are front and center on a barrel-heavy nose. This feels a bit choppy, with astringent tannins. Herbal salty plum flavors wear a lot of oaky makeup, while this finishes with a forced woody flavor.', 86, 12.0, 'Rapel Valley'], 
 [90, 'US', "This blend of Sangiovese, Malbec, Cabernet Sauvignon, Petite Sirah and other varieties plays well to type. It shows a wealth of ripe, dusty black fruit that's richly round and soft on the palate, approachable and lightly oaked.", 88, 23.0, 'California']
]

import pandas as pd
import math

df = pd.read_csv('images/ch6/winemag-data.csv')
wine_ls = df.values.tolist()  # 得到数据的二维列表
# print(wine_ls[:3])  # 查看二维列表

# 1. 用列表推导式，得到所有的国家列表
countries = [i[1] for i in wine_ls]
print(countries[:10])
print(set(countries))
print(sorted(set(countries)))

# 2. 用列表推导式，得到所有的酒的评分的平均分
points = [i[3] for i in wine_ls if not math.isnan(i[4])]
print(sum(points) / len(points))

# 3. 用列表推导式，得到所有的酒的价格的平均价
prices = [i[4] for i in wine_ls if not math.isnan(i[4])]
print(sum(prices) / len(prices))

scores = []                      # 创建空列表
with open('5.1 score.txt','r',encoding='utf-8') as data:
   for line in data:             # 遍历文件对象
      scores.append(int(line.strip().split()[1]))      
print(scores)                    # 输出列表

# 列表推导式实现
with open('5.1 score.txt','r',encoding='utf-8') as data:
   scores = [int(line.strip().split()[1]) for line in data]
print(scores)                    # 输出列表

# 方法一
n = int(input())
for num in range(10**(n-1),10**n):  # 遍历所有n位数
   sumOfnum = 0
   for i in str(num):       # num转为字符串，对其中的数字进行遍历,i为字符串
      sumOfnum = sumOfnum + int(i) ** n      # i转整数，计算其n次方累加
   if sumOfnum == num:                       # 若累加和与num值相同，是素数
      print(num)                             # 输出找到的素数

# 方法二
n = int(input())
ls = [x ** n for x in range(10)]        # 推导出0-9中每个数的n次方存于列表
for num in range(10 ** (n - 1),10 ** n):  # 遍历所有n位数
   if num == sum([ls[int(i)] for i in str(num)]):    
      print(num)         # 输出找到的素数

def isNarcissus(num):
    """接收一个n位正整数为参数，判定其各位上数字的n次方的和是否与该数相等，返回布尔值"""
    return num == sum([int(i) ** len(str(num)) for i in str(num)])

print(*[i for i in range(10, 100000) if isNarcissus(i)])
# 153 370 371 407 1634 8208 9474   

print(*[num for num in range(10, 100000) if num == sum([int(i) ** len(str(num)) for i in str(num)])])

print(*[x for x in range(2, int(input())) if not [y for y in range(2, x) if x % y == 0]])

g = ( i ** 3 for i in range(11))
print(type(g))                   # <class 'generator'>，g的数据类型为生成器
print(g)  # g是生成器对象，<generator object <genexpr> at 0x00000202A663DC00>
print(list(g))# 转为列表可输出[0, 1, 8, 27, 64, 125, 216, 343, 512, 729, 1000]
print(list(g))                    # 生成器对象被遍历后会变成空 []
g = ( i ** 3 for i in range(11))  # 重新创建生成器对象
print(next(g))                    # 输出 0
print(g.__next__())               # 输出 1
print(next(g))                    # 输出 8
print(list(g))       # 转为列表可输出[ 27, 64, 125, 216, 343, 512, 729, 1000]